I saw a conference organiser do something very interesting on LI the other day. He posted a short video where he offered to send a lottery ticket (he was holding them in his hand) to everyone who tagged a potential attendee for his event.
He had dozens of comments within hours with people tagging people they thought might want to register.
I will follow up with him to see how many converted and whether the leads were each worth £2.50 (plus postage I guess!).
Anyone seen anything similar which might work in a business to business context?